Androgen receptors were measured in transitional cell carcinoma tissues obtained from 13 patients with bladder tumours and 3 patients with ureteric tumours. Scatchard analysis of binding of mibolerone, a synthetic androgen, was used for receptor measurement. None of the patients were receptor positive. This study suggests that human male hormones do not play any direct role in the malignant transformation of human transitional cell epithelium.